The present invention relates to the general field of aviation. It applies more particularly but in non-limiting manner to turbine engines, and in particular to turbojets.
More particularly, the invention relates to measuring operating parameters of an aircraft engine, such as for example the pressure of a gas stream flowing in the engine.
In known manner, an aircraft engine is controlled and regulated on the basis of measurements supplied by dedicated computers of the aircraft and based on sensor technologies that are known for their stability and for their accuracy. This applies in particular to atmospheric pressure, written P0, which is supplied by a computer dedicated to atmospheric parameters (known as an “air data computer”), e.g. making use of sensors of the quartz type or of the vibrating cylinder type that present long-term accuracy.
For simplification purposes, in the description below, the term “aircraft measurements” is used to designate pressure measurements provided by these dedicated computers of the aircraft.
The aircraft measurement of atmospheric pressure is used by the full authority digital engine control (FADEC) unit, in particular for controlling the thrust of the aircraft engine. Given the importance of this parameter, the FADEC also has an atmospheric pressure measurement available that is performed by another sensor, which sensor is in the engine computer of the aircraft.
This measurement referred to below as the “engine measurement” (in contrast to the aircraft measurement) is used in the event of aircraft measurements of atmospheric pressure being lost in order to limit variation in the thrust of the engine. It must therefore be accurate, and it is the subject of draconian regulations concerning the maximum thrust variation that can be allowed to occur in the event of aircraft measurements being lost.
In order to comply with these regulations, a first solution that engine manufacturers have considered consists in having recourse to engine sensors that present good performance, i.e. close to that of aircraft sensors. Nevertheless, such sensors are very expensive because of their accuracy.
Furthermore, sensors in the engine are subjected to a thermomechanical environment that is much more severe than that to which aircraft sensors are subjected. Consequently, as a general rule, it is very difficult to guarantee that the performance of such sensors will be stable for use over a long duration.
It is thus common for an engine sensor that has been in use for several years to present a significant amount of drift error (also known as “zero error” or as “offset”). Since the sensor is required to continue complying with the regulations in force in spite of this significant drift error, it is necessary for its accuracy when new to be very great so as to ensure that it remains within its tolerance margin for as long as possible.